This invention relates in general to electrical switches, and more particularly to a switch which upon being actuated establishes positive contact.
Aircrafts have a wide variety of electrical switches, one type requiring the detonation of an explosive to change its condition. These switches are often employed in emergency escape systems, for they provide a quick and positive means for opening doors or ejecting personnel. The typical explosive-operated switch includes a body into which the explosive discharges, and this body contains a piston which is normally held in a fixed position by a single shear pin. However, when the explosive is detonated, the force generated by it shears the pin and drives the piston through the body. The piston in turn causes a slide to change position within the body. Both the body and the slide have contacts embedded within them, and the change in position for the slide results in a different alignment of contacts between the body and slide. The body also has a standard pin-type connector on it, with the pins of the connector being connected to the contacts of the body by wires that are soldered to their respective pins and contacts.
The typical switch is not altogether satisfactory for aircraft or other applications. First, its assembly requires a considerable amount of manual labor inasmuch as the wires between the pins and the contacts of the body must be placed and soldered or otherwise secured by hand. Secondly, the wires themselves present operational problems in that they are subject to fatigue and hence breakage, they may not be adequately secured, or they may lose their insulation. The wires also require an access opening in the switch body, and this opening is usually closed by a cover plate that is welded in place. As a consequence the switch cannot be taken apart for inspection. Aside from that, the shear pin tends to cause the slide to skew initially in the chamber, and this in turn can cause contact bounce with its attendant voltage fluctuations. Furthermore, the switch has no locking feature, but instead relies on friction between the slide and body to hold it in its actuated condition, which is not an entirely reliable arrangement. In addition, the aligned contacts on the slide and body normally establish electrical contact at only one location, or point, along their opposing surfaces.